The invention relates to annular shaft seals and particularly those of the type that during installation must be moved over a first, larger diameter portion of the shaft for sealing against a second, smaller diameter portion of the shaft.
Shafts of the foregoing type frequently have splined areas which have a larger diameter than the adjacent smooth surface of smaller diameter against which the seal is created. Shafts of this type are used in connection with yokes for motor vehicles and other applications. Heretofore the seals have been made with a split cork gasket compressed by a screw cap. More recent prior art seals have used elastomeric seals such as shown in U.S. Pat. Nos. 4,114,897 and 4,126,317. In those patents it was necessary to hold the sealing lip in a non-sealing configuration out of contact with the larger diameter splined portion of the shaft. This was accomplished by either folding the sealing lip over the outside of the seal or folding the sealing lip to the inside of the seal during installation and thereafter reversing the position of the sealing lip so that it would be in contact with the smaller diameter portion of the shaft. In such prior art seals it was necessary to severely stretch the sealing lip from its final sealing diameter to a substantially larger diameter during assembly so as to prevent the sealing lip from being damaged by the splined portion of the shaft. Also in such prior art seals the seals were pointed away and toward the control of foreign material from the smooth, smaller diameter of the shaft.
It is an object of the present invention to overcome the foregoing disadvantages and to provide a seal that is structurally pointed in the direction to keep the grease retained within the yokes and the splined area of the shaft. It is a further object of the invention to provide an annular shaft seal having a protected primary shaft sealing lip backed up with a secondary sealing lip to offer extra protection to preserve the sealing action of the primary sealing lip.